The melting point notion is throwing you off -- manufacturing new aluminum requires way more energy than glass. The reason people will pay you to recycle aluminum is because of the huge differential in (electricity) cost between making new aluminum vs. recycling aluminum. The energy differential between making new steel vs recycling steel is about 2:1. For aluminum, it's 20:1. This is because making aluminum involves first melting bauxite ore, then running a shit-ton of current through it to perform electrolysis.